Pure-tone audiometry in otosclerosis: insufficient evidence for the diagnostic value of the Carhart notch.

Objective: To evaluate whether the Carhart notch on pure-tone audiometry is reliable as a diagnostic test for predicting otosclerosis in patients with conductive hearing loss. Data Sources PubMed, Embase, the Cochrane Library, CINAHL, and Scopus.

Methods: A systematic search was conducted. Studies reporting original study data were included. After assessment of directness of evidence and risk of bias of the selected articles, the prevalences and the positive and negative predictive values were extracted.

Results: A total of 1402 unique studies was retrieved. Three of these satisfied the eligibility criteria. One study provided direct evidence, while all studies carried moderate to high risk of bias. One study with moderate directness of evidence and high risk of bias was not further analyzed. In a study with a high directness of evidence, a high risk of bias, and a low prevalence of otosclerosis (8%) in patients with conductive hearing loss, the presence of a Carhart notch at 2000 Hz increased the risk of otosclerosis with 33%. In a second study with moderate directness of evidence, moderate risk of bias, and a high prevalence of otosclerosis (72%) in patients with a surgically confirmed congenital ossicular anomaly or otosclerosis, the presence of a Carhart notch at 2000 Hz increased the risk of otosclerosis with 2%.

Conclusion And Recommendation: Although there is insufficient high-quality evidence regarding the diagnostic value of the Carhart notch, it seems it is a useful hint for the presence of otosclerosis, but it cannot be used to confirm a diagnosis of otosclerosis.